JIM Murphy has insisted that he can still become First Minister next year despite presiding over a catastrophic defeat at the hands of the SNP and voices within his party calling for him to quit.

The former MP, speaking hours after he lost the East Renfrewshire seat he had held since 1997, claimed that he was proud of a Scottish Labour campaign he described as "energetic and professional" and a "radical" manifesto but said his party had been overwhelmed by "history and by circumstances."

However, despite his insistence that he will fight on, his future looks increasingly uncertain amid claims that his position has become untenable. One senior figure within Scottish Labour, who backed Mr Murphy for the party leadership in December, said he should do "the decent thing" and step aside.

He added: "How can Jim think he can go to Holyrood when he said he wouldn't lose any seats or be outmanoeuvred by the Nats? Everything he said will be constantly played back to him.

"He'll be hoping to pull down the hatch and for it all to go away and surround himself with the Better Together crew. It won't. No malice to him but the idea he hangs around and keeps up messages about 'the working class' and believes charisma is all he needs, well it worked for her [Nicola Sturgeon]. It didn't for him."

He added: "Maybe the decent thing to do is hand things over to Kez or even Ian Murray until he's at Holyrood. Who's paying him? Don't know. That's another unanswered question."

It follows Ian Davidson, the former Labour MP who lost his Glasgow South West seat in an SNP landslide, saying that Mr Murphy had a "moral responsibility" to stand down after leading his party to "the biggest ever disaster that Labour has suffered in Scotland." Andy McFayden, a former Labour spin doctor, said he struggled to see how he had the "legitimacy and credibility" to carry on.

However, he remained defiant at a morning press conference at Scottish Labour's Glasgow headquarters. Other party figures publicly backed his desire to stay on, with Michael McCann who lost his East Kilbride, Strathaven and Lesmahagow seat in a landslide, saying the huge SNP surge was no reflection on any individual.

Mr Murphy, flanked by his deputy Kezia Dugdale, said: "We make no excuses, a party can never blame the electorate, but we found ourselves hit by the perfect storm of three really significant factors.

"Firstly, the simple maths of a Yes vote finding a home in one party versus a No vote spread across three political parties. It is clear that it will be some time before the divisions of the referendum fade into distinction between traditional left and right wing politics in Scotland.

"Secondly, we were hit by two nationalisms, a Scottish nationalism reassuring people that they could vote SNP and get Labour, and an English nationalism, stoked up by David Cameron, warning 'vote for Labour and you will get the SNP'.

"Unsurprisingly, forced into an artificial contest between English nationalism and Scottish nationalism, many Scots, including many No voting Scots, chose the SNP.

"The third factor is of course the long standing problems that led me to stand for leadership of this remarkable party in the first place.

"We had for too long lacked a clear message, a clear offer, and a continuity of leadership - five leaders in just seven short years."

He added: "We didn't have the time nor space to turn that round in that short period.

"Some have said it was an impossible task to turn around all those years of gradual decline in five short months. But it hurts never the less."

He confirmed that party rules allowed him to stay on as leader, despite no longer being a parliamentarian, and would stand for election to the Scottish Parliament.

Mr Murphy said that while the SNP had not won a mandate for a second referendum, "competing nationalisms on both sides of a non-existent border does threaten the United Kingdom."

Asked whether his party could become fully autonomous from UK Labour as he sought to rebuild, he did not rule it out, saying: "We'll reflect on what yesterday's result means for Scotland and the Scottish Labour Party rather than rush into any judgement."

Whether Mr Murphy would be paid a wage by Scottish Labour remained unclear last night. A senior party source said: "Obviously he gets a resettlement grant from the House of Commons as all defeated MPs do. He's now a private individual, his financial arrangements are a matter for him."